In general, congenital cardiac diseases such as ASD have been treated by a surgical operation. As a matter of course, such a surgical operation includes not only treatment of the affected part but also thoracotomy or laparotomy and causes significant damage to a patient. In particular, it causes serious damage to child patients who are poor in physical strength.
Recently, a non-operative method for occlusion of atrial septal defects has been developed, in which a cardiocatheter is transvascularly inserted into the heart. This method is known as a percutaneous transluminal therapeutic catheterization, and the first clinical success in this method was reported in 1976 by King and Mill. In the method of King et al, an atrial septal defect is closed by introducing a pair of umbrella-like members for the left atrium and the right atrium into the atria with an insertion tool composed of a double-layered catheter and a core wire coaxially arranged therein, placing the members on the opposite sides of the defect, and locking them together at a central hub which crosses the defect.
However, this method requires the use of a very large-sized insertion tool and hard umbrella-like members, thus making it impossible to apply it to children, especially to preschool children. For this reason, as a result of efforts to miniaturize such a device, Rashkind developed a single-umbrella type plug having a hook and succeeded in clinical application of the device to a child in 1977. However, this method has a defect that the plug is sometimes hooked on an unintended side of the heart because of being provided with the hook. Once the umbrella-like member is opened, it is impossible to change the hooked position as well as to draw back the device from the heart. This requires an emergency surgical operation when the plug is hooked on an unintended side of the heart. In order to overcome such disadvantages, Rashkind further developed a plug comprising two umbrella-shaped occluders having eight stainless steel struts and being connectable to each other. The device has been put into clinical use widely for occlusion of patient ductus arteriosus.
Japanese unexamined patent application No. 5-237128 filed by James E. Lock et al. discloses an interatrial occlusion device comprising two umbrella-shaped members composed of eight stainless steel struts as in Rashkind's device, each strut being provided at a central part thereof with a spring coil. This device is firmly fixed to the thin interatrial septum by closely adhering the two umbrella-shaped members to each other in an overlapping state. This device is called a clam shell-shaped interatrial occluder because of its configuration similar to that of a clam being a bivalve. The procedure is carried out by inserting an elongated sheath with a thickness of 11 French through the femoral vein. This device has been widely used for closing atrial septal defects by means of percutaneous transluminal therapeutic catheterization since the device can be applied to patients with a weight of 8 kg and above.
However, there is a limitation to the application of these occlusion plugs since only occlusion plugs with a uniform shape are prepared for various configurations of atrial septal defects and since the occlusion of a defective opening or hole requires use of an occlusion plug twice the size of the defective opening or hole. These devices therefore, can be applied only to relatively small defective openings or holes present in the central part of the atrioventricular septum. In addition, there is a fear of bad effects due to use of occlusion plugs since there is no data on long-term use of occlusion plugs left in the heart.
The present inventors have already proposed a catheter assembly for intracardiac suture, which is applicable to various configurations of ASD and can percutaneously sew and close ASD, as disclosed in Japanese unexamined patent application No. 7-171173. This catheter assembly comprises a piercing member and a tabular member. Using this catheter assembly, the piercing member is placed at the edge of the defective opening or hole in the heart, and the defective opening or hole is closed by the tabular member.
This catheter assembly is advantageous in that it is applicable to various configurations of ASD, but is disadvantageous for the following reasons. In the method using this catheter assembly, since a piercing member having a sharp edge at a distal end is pierced into the edge of the defective opening or hole in the heart and since the tabular member is left in the heart for a long period of time to close the defective opening or hole, the method will be accompanied by some postoperative problems. In addition, since the tabular member must be large so that it can close the defective opening or hole, a large foreign substance is left in the body after the operation. For these reasons, further improvements in the catheter assembly to improve its safety have been desired.